如何在Django中编写自己的装饰器？ [英] How can I write my own decorator in Django?

问题描述

我的 models.py 文件如下：

My models.py file is as follow:

from django.contrib.auth.models import User

class Shopkeeper(models.Model):
    user = models.OneToOneField(User, on_delete=models.CASCADE, primary_key=True)
    # ...


class Customer(models.Model):
    user = models.OneToOneField(User, on_delete=models.CASCADE, primary_key=True)
# ...

我有一些视图，只有客户可以登录后访问，但店主无法访问。反之亦然。
如何为此类任务编写装饰器？

And I have some views which only Customers can access after login, but Shopkeepers cannot. And vice versa. How can I write decorator for such task?

推荐答案

装饰器没有什么神奇之处，它是一个函数将要装饰的函数（或类）作为输入，并对其进行一些更改。如果我们查看 login_required 装饰器[GitHub] ，我们看到：

There is nothing magical about a decorator, it is a function that takes as input the function (or class) to decorate, and makes some changes to it. If we look at the login_required decorator [GitHub], we see:

def login_required(function=None, redirect_field_name=REDIRECT_FIELD_NAME, login_url=None):
    """
    Decorator for views that checks that the user is logged in, redirecting
    to the log-in page if necessary.
    """
    actual_decorator = user_passes_test(
        lambda u: u.is_authenticated,
        login_url=login_url,
        redirect_field_name=redirect_field_name
    )
    if function:
        return actual_decorator(function)
    return actual_decorator

因此，我们实际上可以简单地制作 user_passes_test 装饰器的特殊情况：

We can thus actually simply make a special case of the user_passes_test decorator:

from django.contrib.auth.decorators import user_passes_test

def shopkeeper_required(function=None):
    def is_shopkeeper(u):
        return Shopkeeper.objects.filter(user=u).exists()
    actual_decorator = user_passes_test(is_shopkeeper)
    if function:
        return actual_decorator(function)
    else:
        return actual_decorator

def customer_required(function=None):
    def is_customer(u):
        return Customer.objects.filter(user=u).exists()
    actual_decorator = user_passes_test(is_customer)
    if function:
        return actual_decorator(function)
    else:
        return actual_decorator

然后您可以实现它如：

@login_required
@shopkeeper_required
def some_shopkeeper_view(request):
    # ...
    pass

@login_required
@customer_required
def some_customer_view(request):
    # ...
    pass

请注意，此 @shopkeeper_required 不会 确实要求用户登录，尽管在很多情况下都是这样。

Note that this @shopkeeper_required does not really enforces that the user is logged in, although in many cases that will be the case.

EDIT ：

我们可以将其与 @login_required 合并（通过添加一个参数来作为打开或关闭此行为的开关，默认启用），例如：

We can merge this with a @login_required (by adding a parameter that acts as a switch to turn this behavior on or off, by default on), like:

from django.contrib.auth.decorators import user_passes_test

def shopkeeper_required(function=None, login_required=True, redirect_field_name=REDIRECT_FIELD_NAME, login_url=None):
    def is_shopkeeper(u):
        if login_required and not u.is_authenticated:
            return False
        return Shopkeeper.objects.filter(user=u).exists()
    actual_decorator = user_passes_test(
        is_shopkeeper,
        login_url=login_url,
        redirect_field_name=redirect_field_name
    )
    if function:
        return actual_decorator(function)
    else:
        return actual_decorator

def customer_required(function=None, login_required=True, redirect_field_name=REDIRECT_FIELD_NAME, login_url=None):
    def is_customer(u):
        if login_required and not u.is_authenticated:
            return False
        return Customer.objects.filter(user=u).exists()
    actual_decorator = user_passes_test(
        is_customer,
        login_url=login_url,
        redirect_field_name=redirect_field_name
    )
    if function:
        return actual_decorator(function)
    else:
        return actual_decorator

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